Currently the Wikimania wiki (wikimania.wikimedia.org) allows local file uploads by any confirmed user.
Ideally all uploads of freely licensed material should go to Commons instead and local uploads be limited to non-free content (e.g. sponsor logos etc.). One of the most efficient ways of ensuring this is to remove the upload/reupload right from Confirmed_users and Autoconfirmed_users and only have it for Administrators.
Since the main responsibility for the wiki will shift from year to year it might additionally be convenient to set up an Uploader group which trusted users can be added to without necessarily making them administrators.